A review of the problem of the long-term uncontrolled growth of man-made objects in earth orbit is presented. After a discussion of the main underlying concepts, the relative effectiveness of the adoption of some mitigation measures over 100 – 200 years is analysed, including the minimisation of mission related objects release, the on-orbit explosion avoidance and the de-orbiting of spacecraft and upper stages in low earth orbit. It is shown that only the implementation of the full set of mitigation measures discussed would be able to guarantee the long-term approximate stabilisation of the population of large objects, maintaining at acceptable levels the growth of millimetre and centimetre sized debris.